The invention pertains to a railroad frog for switch points and crossings. This type of frog is known from EP 0,282,796. As in all known frogs, the wing rails are separated from the frog point by filling plates in order to ensure the proper flange groove width. To guarantee a certain elasticity of the individual components of this frog, a bushing is passed through the frog with play, where this bushing is supported on both sides by the spacer element on the filling plates, which in turn lie on the fishplate seating surfaces of the wing rails. The wing rails are tightened together with a bolt, so that the filling plate, the spacer element, and the bushing thus together form a rigid unit. Only the frog point can move horizontally and vertically relative to the two wing rails with the stipulated amount of play. The two wing rails and the frog lie on a ribbed plate, which has vertically protruding ribs that serve as stops for the feet of the wing rails and the frog point for horizontal movement and permit the desired horizontal mobility based on the stipulated horizonal.
WO 94/02683 discloses a frog that is assembled from two unwelded rail sections screwed together via filling plates and a bolt that passes through the connector of the wing rails and the frog. To keep both unwelded rail parts of the frog point in a defined position relative to each other, the rail sections of the frog are penetrated without play by a bushing, or the opposing surfaces of the frog section are joined by a profile or indentation running in the longitudinal direction whose tooth flanks lie against each other without play.
A frog similar to EP 0,282,796 is also known from EP 0,281,880 B1 and DE 37,08,233 A1.
Simple, rigid frogs are generally arranged in switch points at the places where the inner wheel flange intersects the two treads in the crossing region for problem-free traversal. The wheel rims are so wide that they cover the groove width and the width of the still load-bearing point of the frog point. During the free passage of the flange, the wheel rims that transfer the wheel load must allow problem-free traversal over intersecting treads without destruction of the narrow frog point.
The rigid, simple frogs assembled from rails with the three main parts (i.e., the two wing rails and the single frog point) are bolted together via filling plates, which is also intended to prevent longitudinal shifting due to temperature fluctuations and braking. These threaded joints of the rigid, simple frogs now designed as HB (high-strength, bolted) threaded joints exhibit significant technical deficiencies, as well as very high manufacturing and maintenance costs, which adversely affects service life. The very high manufacturing costs are primarily attributed to the fact that filled section rails of the corresponding rail profile are used for the point instead of the standard rails otherwise common on the track at switch points. In order to be able to weld the welding cross section of the two points consisting of filled section rails, both the main point and the wing rail must be machined generally up to at most halfway in the critical region. Before welding these two cross sections into a single frog point, the area being welded must be preheated to about 400-500xc2x0 C. so that no cracks form during welding of the highly carburized rail steel. This temperature must be maintained throughout welding. However, it is generally not held at this level, so that martensite formation occurs in the welding area and the welds crack, even after a short time, or the point rails break, which today is still, unfortunately, very often the case.
Moreover, the region of transfer of the wheel from the wing rail to the point or vice versa is often hardened or pearlitized in order to reduce wear. Decarburizations that lead to lower strength of this area, however, develop in the initial and end region during hardening or pearlitization, which in practice leads to increased maintenance costs due to so-called switch dents after brief operation.
It is also known from DE 33,39,442 C1 that the frog point can be provided with a recess in the region of the greatest wear, especially in the initial region, into which a frog insert made of high-carbon manganese steel is firmly fitted. The high-carbon manganese steel is secured by a press-fit produced by a low-temperature shrinkage process. This process does lengthen the service life of the frog point, but is very complicated and expensive and creates an almost inelastic frog point.
Holes can be drilled through both the frog block and the wing rails, which, on the one hand, entails high costs and, on the other, leads to rail breaks if the hole edges are not properly deburred. Joining of the filling plate support surfaces with the fishplate seating surfaces of the wing rails as free from play as possible requires high manufacturing costs. The main cause of high wear, and thus relatively short service life, is the unduly high rigidity of the transitional region of the wheel from the wing rail to the point and vice versa because of the unduly compact cross section, i.e., the total moments of inertia about the X axis, the combination of wing rail, frog points and filling plates. It was already recognized in EP 0,282,796 that these problems could be solved by greater elasticity than before, i.e., by a relative vertical displaceability between the frog point and wing rail so as to support only limited forces in the weak region of the frog point and high forces in the regions of greater rail cross section. Owing to the fact that both wing rails are still rigidly coupled via the frog point, their moments of inertia are still relatively high. The frog point is also mounted there to achieve a bending rod function, like a jib, i.e., its free end can be deflected vertically, whereas the rear region is rigidly fixed. The front region of the frog point thus bends downward when traversed and the tread is stressed in the region where the train is located, which has led to rail breaks even after a short period of operation.
If one compares the inertia, i.e., the moment of inertia of the transitional region of two wing rails, two filling plates and, if necessary, the filled section rail points, it can easily be seen that this type of transitional region acts like a rigid block that causes compressive deformation in the impact region because of its rigidity. If we further consider that railroad wheels are not perfectly round, which is caused possibly by the high rigidity of the impact point and pointlike or even bluntly run-over single frogs, it becomes clear that this is an additional major cause of wear. To eliminate this wear due to orthogonal compressive deformation on the frog point and the wing rails during operation, both the point and the wing rails are resurfaced by welding under practical conditions on the track. This resurfacing by welding is often not carried out skillfully, especially if the weld is not sufficiently preheated, which results in the frog breaking by martensite formation after a short time and its replacement.
The horizontal rigidity, which corresponds to a multiple of that for a single rail because of the very high moment of inertia of the entire rim frog about the Y axis, also excessively loads the guardrails. In order to reduce wear on the guardrails, the wing rails should be designed to be horizontally elastic, especially on contact with the rear wheel sets of the wheels.
The greatest tracking defect of current frogs lies in the fact that the wing rails are not cambered in accordance with the conicity of the form of the running wheel. Thus, during traversal of the point the axle of the wheelset at the equal height wing rails is significantly lowered vertically and thus strongly accelerated vertically. The wheel contact surface point then wanders farther from the running edge to the smaller diameters of the rim, which results in significantly lower circumferential velocity of the wheel on the frog side, whereas the wheel of the wheelset on the inner curve runs on a larger diameter of the wheel contact surface point because the wheelset is pulled toward the guardrail. This phenomenon can also be viewed as a paradox, since, because of the guardrail, the wheel running on the outside of the arc runs over a much smaller diameter than the wheel running on the inside of the arc.
Since the current frog point is lowered into a tread that tapers off to a point opposite the running direction upon passing over the point when the wheelset goes from the wing rail to the rigid frog point, in addition to the sudden change from smaller to larger diameter wheel contact surface, i.e., to a much greater circumferential velocity, it is also opposed to the previous direction of acceleration, namely xe2x80x9ccatapultedxe2x80x9d not downward, but obliquely upward in the opposite direction. This is the reason for plastic compressive deformation of the tread of the point and probably also the reason for ovalization of the wheel, both for the wheelset and for the impact point on the rigid frog point.
Concerning the elasticity of the previous frog design, it can be stated that the frog generally cast from high-carbon manganese steel and used for more than 100 years, as well as the bolted frog, lies in the switch point practically like a rigid block, i.e., like a foreign body. There is not even a roughly adequate elastic design that would accommodate the elasticity of the standard rail. In bolted frogs, the crossover area generally still lies on a tie, which further increases the rigidity. For this purpose the filling plates are also still arranged in this area so that the moment of inertia about the X axis, which is decisive for elastic vertical bending of the frog point, is roughly more than five times that of a standard rail in the impact cross section. It behaves similarly or even more poorly during traversal from the wing rail to the frog point in cast frogs, and this is even worse in block frogs, because the moment of inertia there is not only five times, but often more than ten times that of a normal standard rail.
All of the aforementioned deficiencies and drawbacks of the simple rigid frogs known thus far, primarily:
vertical and horizontal rigidity, i.e., unduly limited vertical and horizontal elasticity;
very significant material waste;
wasting of resources;
unduly limited availability of rigid frogs;
unduly high maintenance costs;
unduly high new prices;
no easily-correctable camber;
inappropriate joining and resurfacing welding and many more, are avoided by the present invention.
The primary object of the invention is to improve the frog of the initially mentioned type, so that with lower manufacturing and material costs a longer service life and greater availability of the frog is achieved in the operating track.
Other objects and features of the present invention will be in part apparent and in part pointed out hereinafter by the features stated in the patent claim. Advantageous embodiments and modifications of the invention can be discerned from the subordinate claims.
The invention proceeds from the recognition that the three main components, i.e., two wing rails and a frog point, can be fully disconnected from each other with respect to their mass or moment of inertia if the filling plates and their threaded joints are eliminated. Because of this, not only is each of the three main parts (two wing rails and a frog point) fully decoupled from the other parts, but additional weight is saved by eliminating the filling plates and threaded joints, thereby further reducing the moment of inertia. The relative position of these three main parts in the horizontal direction is ensured by vertically protruding ribs of a ribbed plate, between which the main parts are held essentially free of play (within narrow tolerances). Vertical elastic attachment of the three main parts occurs by elastic tensioning clamps that tighten the three main parts elastically and vertically only in the plate region. The groove width is guaranteed by the ribs of the ribbed plate and by corresponding machining of the feet and heads of the wing rails and the frog point. The ribbed plates in turn are attached to ties, preferably bolted. Owing to the fact that each of the three main parts can undergo essentially elastical and vertical deformation independently of each other, the previously very high impact when the wheel rim passes from the wing rail to the point or vice versa can be sharply reduced, so that the previous wear due to compressive deformation on the rigid frog point and wing rails is significantly reduced, generally even fully eliminated.
Another important aspect of the invention is that the frog point consists of standard rails that are welded together on the head and foot over the length of the frog point.
According to a modification of the invention a particularly elastic spacer is inserted between the foot of the wing rail or the frog point and the contact surface on the ribbed plates. Thus, each of the three main parts can oscillate with a corresponding natural frequency, which thereby increases elasticity, improves travel comfort, and significantly lengthens the service life.
According to a modification of the invention, in addition to these elastic spacers, spacers of different thickness are possible. Because of this, by insertion of these additional spacers with a specified thickness under the corresponding foot region of the wing rail or the frog point the desired greater height of the traversed surface can be adjusted very exactly without problem. Any wear that has appeared can also be equalized without having to conduct resurfacing welding with subsequent reprofiling of the tread in the region of resurfacing. Maintenance costs can thereby be substantially reduced and, above all, the availability of the object of the invention is raised almost to 100% of its service life in the operating track.
According to the prior art, only the external foot regions of the wing rails have thus far been elastically tightened vertically by anchor clamps or other tightening elements relative to the ribs, in which the tensile forces per tightening side amount to a maximum of 10-15 kN.
According to a modification of the invention, the internal regions of the wing rails and both external foot sides of the frog point are now also tightened by elastic anchor clamps, etc., in which tensile forces of 10-15 kN per tightening point are preferably achieved. Thus, the three regions (frog point and two wing rails) are each tightened as much as the enrim rigid frog used to be. Because of this advantage, the necessary rail anchor, which is supposed to prevent relative shifting of the wing rails and frog point in the longitudinal direction of the rails, turns out to be much more economical and lighter. This type of rail anchor is further described in the subsequent description.
When totally worn out or broken, the wing rail and/or frog point can be easily and quickly replaced, which substantially increases the availability of the object of the invention in the operating track.
The previous service life of rigid, highly loaded, single frogs is, from experience, 3 to 4 years, depending on the load, sometimes even slightly longer. The service life can be substantially increased with the invention, since there are no weak points in either the design or in welding of the two point rails that form the frog point, so that the total cost of a new installation is quite modest relative to the current state of the art.
Another major advantage of the invention lies in the very simple and economical disposal of the frog point or one or both wing rails.
Switching devices, which generally have rigid, single frogs for economic reasons, are often used around residential areas. Because of the completely elastic support points of the wing rails and frog point, sound emissions can be sharply reduced.
Another particular advantage of the invention lies in the easy height adjustability of the treads of the two wing rails, but also the frog point, as compensation for vertical wear and also the rail anchor. Adjustment to the anchor clamps used thus far in tracks and switch points of the xe2x80x9cSKLxe2x80x9d type common in Germany poses no problem. The contact points of the anchor clamps in the invention are essentially at the same height, in contrast to the ordinary SKL anchor clamps, in which the two contact points are at different heights. In order to reduce the guide force, especially during curved travel between the two wing rails and the two point rails, but also between the frog point and the two wings, the three main components are tightened vertically and elastically with slightly modified anchor clamps in the region of the corresponding support point. Since foot areas of essentially equal height are present between the two wing rails and the two point rails as well as between the two wing rails and the frog point, the known anchor clamps are modified so that the two support areas are at the same height. In this way, the costly filling plates that significantly increase the rigidity of the frog are eliminated.
In order to be able to install a frog according to the invention in the shortest possible time at a given location, the frog is delivered to the site with the corresponding ribbed plates already installed. A single, rigid frog optimized in every respect can thereby be installed without problem in the shortest time possible. Spare parts, like the two wing rails and the frog point, can be stocked so that almost 100% availability of the object of the invention is provided for railroad operation in the shortest time without significant stockkeeping.
The following should be noted concerning the vertical-elastic tightening of the individual support point areas:
In order to keep the foot width of the two wing rails (inside) but also the frog point (outside) as wide as possible and in order to be able to replace the hook screws when necessary without disassembling the rails, the inner bracing ribs are designed to be narrower and higher (with the same load-bearing capacity) than the outer ribs. The aforementioned foot width is determined according to the standard width of the usual hook bolts employed in the SKL fastening, which is 24 mm, which gives a total width of 24 mm with an air gap of 1 mm on each side of the rib. Since the stability of the frog point depends only on the width of the rail foot in the plate region, the ribbed plates are widened so that they do not arch concavely during tightening and xe2x80x9cpumpxe2x80x9d in operation, are preformed convexly, and are produced from fine-grained steel of higher strength.
For heavy-load switch points the foot should only be somewhat narrowed in the inner plate region for half the rib width. Since the length of the rib is forged from one piece and welded to the base plate, the corresponding foot regions are notched only over a maximum length of 120 mm.
For slightly stressed frogs (for example, for service in outlying suburbs), the two feet can be surfaced or milled over their enrim length corresponding to the rib width, which means cost-effective manufacture.
The most important aspects and advantages of the invention will now be summarized:
Frog and wing rails are connected vertically and elastically to the ribbed plates of the ties by anchor clamps (SKL). The previous block unit of a rigid frog and wing rails is thus reduced to individual rails. These individual rails have an intrinsic elasticity so that the object of the invention behaves almost like a normal track rail in terms of oscillation and damping behavior. The previously used filling plates are no longer used, nor are the threaded joints.
The individual rails are more easily replaceable. Additional plastic spacers can subsequently be incorporated beneath the rails, with which stepless height adjustment of the treads is produced. The previous repair of the wing pieces by resurfacing disappears. Tensioning occurs vertically with anchor clamps. The individual rail feet have about 1 mm air relative to each other laterally in the narrow region. The ends of the two standard rails that pass over the enrim length of the frog point without a welded joint and form the point are welded together over the shortest possible area on the head and foot. Welding methods, such as gas pressure welding, CO2 shielded arc welding, inductive pressure welding, electron beam welding or laser welding, are considered here.
In the wheel transition region from the point to the wing rail and vice versa, the latter is cambered so that the height difference of the present conical wheel-rim profile is compensated.
The frog point consists of two standard rails, for example of the type UIC 60, which are adapted by machining in the region of the points on their head and foot regions to the point geometry corresponding to the narrowing in the region and welded to the head and foot of the thus formed point by means of longitudinal V-type seams or other types of seams.
The front region of the point can also be produced in one piece as a forged or cast molded article and welded to the two frog points welded together on the head and foot.
Since there are significant forces acting in the longitudinal direction on the wing rails and frog point due to the effects of temperature and braking, a so-called rail anchor must be provided between the aforementioned three main parts which prevents longitudinal migration with relative displacement between the frog point and wing rails. This rail anchor is incorporated as close as possible to the wheel transition [region] with the special feature that each connector of the wing rails and the frog point is individually bolted very tight to the parts of the rail anchor.
The adjustment of different wing rail heights is necessary to equalize the wear of the rail heads of the wing rails, especially in the wheel transition region. Eccentric bushings are provided between the screws and enlarged holes in the rail connectors for the rail anchor. The rail anchor is then one-piece on each side.
According to one variant, each rail anchor side is designed in two parts with several contact surfaces in the longitudinal and transverse direction that transfer the longitudinal forces from the point to the wing rail and vice versa. These forces are about 600-800 kN, e.g., in the longitudinal direction. Either additional spacers or spacers of different thickness are used beneath the wing rail feet to compensate for height differences as a result of wear of the wing rail treads.
The two matching parts can be shifted perpendicular to each other for a height adjustment of the rails. They can transfer significant forces over several contact surfaces in the longitudinal direction of the rails which are many times greater than in the rail anchor devices of the prior art common in switch blades. A small amount of play between the contact surfaces can moderate the transferable longitudinal rail forces. Movement can also be limited by contact surfaces with play in the transverse rail direction.
The parts of the rail anchor that mesh with each other like a comb can also be designed trapezoidally.
The invention will now be explained in detail below with reference to embodiment examples with reference to the drawing.